Author Topic: Sorry if this has been addressed already...  (Read 627 times)

Offline Joe

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Sorry if this has been addressed already...
« on: March 23, 2018, 12:40:06 AM »
Hello,

I am having an exhaust leak issue. Whenever I drive the car exhaust fumes are coming into the cabin. My previous mechanic did a smoke test and had me replace the muffler, resonator as well as the collector donut. But I am still getting exhaust smell in the car. I read somewhere that there is some sort of EGR type thing near the manifold. Anyone have any experiences with a stubborn exhaust leak? Thanks.

Joe

Offline AutoCad

Re: Sorry if this has been addressed already...
« Reply #1 on: March 23, 2018, 07:29:23 AM »
Hey Joe, Are you sure its an exhaust leak?? Do you actually hear a leak?? If you do, it should be pretty easy to pin down. (Pay close attention to the heat crossover on the underside of the intake manifold) If not, it might be gases from your road vent tube getting in. Where is the smell coming in from?? Bad door/window seals?? Holes in the floor?       My 2cents.....
Been there and back, in my Cadillac...

Offline Joe

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Re: Sorry if this has been addressed already...
« Reply #2 on: March 23, 2018, 04:01:32 PM »
Thanks for responding. I have no idea where it is coming from. I think I can hear something from the engine compartment, but I am not sure if that is general road noise or there is an actual leak sound. I hear a different pitch or tone when I am hard on the gas, but it's hard for me to tell if that is a normal sound. The car seals up halfway decently. I think it might be coming from the engine compartment through the firewall. Tell me more if you can about the heat crossover. What is that? What is its purpose? Thanks very much!

-Joe

Offline AutoCad

Re: Sorry if this has been addressed already...
« Reply #3 on: March 23, 2018, 06:43:38 PM »
Once I had an exhaust leak issue with my 1960 SDV that I had a hard time finding. After I changed the exhaust manifold gaskets and donuts, I discovered that my heat crossover was cracked. If you do a bit of research you'll find that this is not an uncommon failure. When you engine is cold, a valve located right by the exhaust donut on the exhaust manifold is closed, causing hot exhaust gases to cross on the underside of the intake manifold to the other side. As the engine warms up, the spring that closes the valve gradually expands and opens the valve allowing the gas to run straight thru out the back of the car. It doesn't take much of a crack to cause a pesky leak, and they always get worse. You might be able to get a small mirror between the manifold and valley plate to to take a peak.  The mid/late 50's 365 CI manifolds were the worst for this cracking.  Good luck!!
Been there and back, in my Cadillac...

Offline Joe

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Re: Sorry if this has been addressed already...
« Reply #4 on: March 23, 2018, 09:53:44 PM »
Thanks very much for getting back to me. I read about this issue on a thread once before but it was on a 59. I know the engines were the same 390 displacement, but they look different. So I thought they might have fixed this problem before my 390 was born. I would have thought the smoke test would have shown this issue but maybe it is so minute that it is tough to spot. Thanks again.

Joe

Offline rare eldorado

Re: Sorry if this has been addressed already...
« Reply #5 on: March 24, 2018, 09:00:23 AM »
if you have a lift available ,,with the enjine running hold a rag over the tail pipe exit for as long as you can this will show any leaks ,A second person will be needed to look .Remember the exhaust will be hot.With the pressure build you may have too do this several times.

Offline iCAD

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Re: Sorry if this has been addressed already...
« Reply #6 on: March 24, 2018, 10:42:51 AM »
Thats a good call, too.....
At a gas station the other day, a guy asks me "what kinda gas mileage do you get with a big old car like that?". "Who cares?" I replied, "it's a Cadillac!!"

Offline Joe

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Re: Sorry if this has been addressed already...
« Reply #7 on: March 25, 2018, 12:09:20 AM »
Thanks very much for your suggestions. I brought the car to the mechanic today. He showed me a small oil leak from the valve cover dripping onto the exhaust manifold that I didn't notice before. Although I don't think that is the smell I am smelling I am having him replace both valve cover gaskets as well as the exhaust manifold gaskets and the collector donut. Hopefully this will shore up any leaks. Thanks again for all your responses. They are much appreciated.

Joe

Offline Joe

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Re: Sorry if this has been addressed already...
« Reply #8 on: March 26, 2018, 11:20:31 PM »
Thanks everyone for your insight. The mechanic replaced the manifold gaskets and a leaking valve cover gasket as well as the donut in the collector. My wife drove the car home with the windows up and said the exhaust smell is gone and she wasn't asleep by the time she pulled it into the garage. Thanks again for all your help. Problem Solved!

Joe

Offline AutoCad

Re: Sorry if this has been addressed already...
« Reply #9 on: March 27, 2018, 10:08:17 AM »
All's well that ends well. Happy cruzin'.
Been there and back, in my Cadillac...